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Crotalaria retusa L.
| Family Name: | Fabaceae (Leguminosae) |
| Synonyms: | Crotalaria tunguensis |
| Common Name: | Rattleweed, Shak-Shak, Rattlebox, Wedge-leaf Rattlebox, 吊裙草, 凹叶野百合, 洛苛草 |
Name
Classifications and Characteristics
| Plant Division | Angiosperms (Flowering Seed Plants) (Dicotyledon) |
|---|---|
| Plant Growth Form | Herbaceous Plant |
| Lifespan (in Singapore) | Perennial |
| Mode of Nutrition | Autotrophic |
| Maximum Height | 1.2 m |
Biogeography
| Native Distribution | Assam, Bangladesh, Bismarck Archipelago, Borneo, Cambodia, Southeastern China & Hainan, Comoros, East Himalaya, India, Iran, Java, Kenya, Laccadive Island, Laos, Lesser Sunda Island, Madagascar, Peninsular Malaysia, Maldives, Maluku, Mauritius, Mozambique, Myanmar, Nepal, New Guinea, Oman, Philippines, Rodrigues, Réunion, Saudi Arabia, Somalia, Sri Lanka, Sumatra, Taiwan, Tanzania, Thailand, Vietnam, West Himalaya, Western Australia & Northern Territory, Yemen |
|---|---|
| Native Habitat | Terrestrial |
| Preferred Climate Zone | Tropical |
| Local Conservation Status | Cryptogenic |
Description and Ethnobotany
| Growth Form | Herbaceous plant with erect growth habit, can grow up to 1.2 m tall. |
|---|---|
| Foliage | Simple leaves, obovate, having a rounded leaf tip and a wedge-shaped leaf base (3.3 - 9.2 cm long, 1 - 3.8 cm wide). They are sessile, spirally arranged and have an entire leaf margin. |
| Stems | Stem is ridged and velvety with short hairs. |
| Flowers | Bright yellow flower consists of 1 large triangular petal hanging over 2 smaller petals that are curled upwards like a hook (1.7 - 2.4 cm long). Flowers are arranged in terminal spike inflorescences located at the branch tips (27 cm long). |
| Fruit | Dry, hairless, cylindrical fruit is known as a pod (3 - 4 cm long). Pod colour changes from greenish to dark brown to black when mature. Shaking a mature pod produces a rattle sound, because the seeds get loose inside. |
| Habitat | Occurs along seashores and dry coastal areas. |
| Cultivation | This species should be planted in fertile, well-draining soil. It is considered an annual plant in temperate regions, but is a short-lived perennial in Singapore, lasting for several years. |
| Ethnobotanical Uses | Others: In East Africa, it is used as a dye plant <1>. Warning: The seeds contain pyrrolizidine alkaloids, such as monocrotaline, which is toxic when consumed by humans <2>, poultry and livestock, such as chicken <4> and sheep <3>. |
Landscaping Features
| Landscaping | This species is planted for its bright yellow flowers. The spirally arranged leaves around an erect stem produces an attractive, symmetrical form. It can be used as a hedge or screen. |
|---|---|
| Desirable Plant Features | Ornamental Flowers |
| Landscape Uses | Parks & Gardens |
| Usage Hazard - Cons | Invasive / Potentially Invasive, Toxic Upon Ingestion |
| Usage Hazard - Cons Remarks | Crotalaria retusa is an invasive and exotic plant species in various countries, such as Brazil <5> and India <3>. It has not been observed to be invasive in Singapore (2026). It contains toxins known as pyrrolizidine alkaloids, as described in the Ethnobotanical Uses field above. |
Fauna, Pollination and Dispersal
| Fauna Pollination Dispersal Associated Fauna | Butterfly Host Plant (Associated with: Lampides boeticus (Linnaeus, 1767)), Bee-Attracting Plant |
|---|---|
| Pollination Method(s) | Biotic (Fauna) (Insects (Butterfly, Moth)) |
Plant Care and Propagation
| Light Preference | Full Sun |
|---|---|
| Water Preference | Moderate Water |
| Plant Growth Rate | Fast |
| Rootzone Tolerance | Moist Soils, Well-Drained Soils |
| Propagation Method Remarks | Propagate by seed or stem cuttings. Seeds should be collected from mature pods that were allowed to dry on the plant. Sow seeds immediately, because they quickly lose viability. |
Foliar
| Mature Foliage Colour(s) | Green |
|---|---|
| Foliar Type | Simple / Unifoliate |
| Foliar Attachment to Stem | Sessile |
| Foliar Margin | Entire |
| Leaf Area Index (LAI) for Green Plot Ratio | 4.5 (Shrub & Groundcover - Dicot) |
Floral (Angiosperm)
| Flower & Plant Sexuality | Bisexual Flowers |
| Flower Colour(s) | Yellow / Golden |
|---|---|
| Flower Grouping | Cluster / Inflorescence |
| Flower Symmetry | Bilateral |
| Inflorescence Type | Spike |
Fruit, Seed and Spore
| Mature Fruit Colour(s) | Black |
|---|---|
| Fruit Classification | Simple Fruit |
| Fruit Type | Dehiscent Dry Fruit , Legume / Pod |
| Mature Seed Colour(s) | Brown |
| Mature Seed Texture(s) | Smooth |
| Seed Quantity Per Fruit | Numerous (>20) |
References
| References | <1> Hanum, I.F. & van der Maesen, L.J.G. (eds) (1997). Plant Resources of South-East Asia No. 11: Auxiliary plants. Leiden: Backhuys Publishers.
<2> Lu, Y.-S., Qiu, J., Mu, X.-Y., Qian, Y.-Z. & Chen, L. (2024). Levels, toxic effects, and risk assessment of pyrrolizidine alkaloids in foods: A review. Foods 13(4):536.
<3> Mallick, S.N., Ekka, N.J., Kumar, S. & Sahu, S.C. (2019). Invasive alien flora in and around an urban area of India. In: Diversity and Ecology of Invasive Plants. London: IntechOpen. Pp. 1–21. https://doi.org/10.5772/intechopen.88725. Accessed 2 Jun. 2026.
<4> Nobre, V.M.T., Dantas, A.F.M., Riet-Correa, F., Barbosa Filho, J.M., Tabosa, I.M. & Vasconcelos, J.S. (2005) Acute intoxication by Crotalaria retusa in sheep. Toxicon 45(3):347–352.
<5> Reis, D.O., Araujo, K.C.T., Silva, F.O., Santos, M.Í.A.G. & Fabricante, J.R. (2022). Distribution of invasive alien species in different scenarios in Brazilian territory. Res. Soc. Dev. 11(3): e54711327072. https://doi.org/10.33448/rsd-v11i3.27072. Accessed 2 Jun. 2026.
<6> Ross, A.J. & Tucker, J.W. (1977) Effects of feeding diets containing Crotalaria retusa L. seed to broiler chickens. The Journal of Agricultural Science 89(1):95–99.
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Image Repository
Others
| Master ID | 596 |
|---|---|
| Species ID | 1891 |
| Flora Disclaimer | The information in this website has been compiled from reliable sources, such as reference works on medicinal plants. It is not a substitute for medical advice or treatment and NParks does not purport to provide any medical advice. Readers should always consult his/her physician before using or consuming a plant for medicinal purposes. |
